1. Field of the Invention
Embodiments of the invention generally relate to a physical vapor deposition chamber.
2. Description of the Related Art
Many semiconductor processes are typically performed in a vacuum environment. For example, physical vapor deposition (PVD) is generally performed in a sealed chamber having a pedestal for supporting the substrate disposed thereon. The pedestal typically includes a substrate support that has electrodes disposed therein to electrostatically hold the substrate against the substrate support during processing. A target generally comprised of a material to be deposited on the substrate is supported above the substrate, typically fastened to a top of the chamber. A plasma formed from a gas, such as argon, is supplied between the substrate and the target. The target is biased, causing ions within the plasma to be accelerated toward the target. Ions impacting the target cause material to become dislodged from the target. The dislodged material is attracted toward a substrate and deposits a film of material thereon.
Generally, two conditioning operations are performed in the PVD chamber to ensure process performance. A first conditioning process is known as burning-in the target. Target burn-in generally removes oxides and other contaminants from the surface of the target and is typically performed after the chamber has been exposed to atmosphere or idled for a period of time. During the burn-in process, a utility wafer or shutter disk is disposed on the substrate support to prevent deposition of target material on the support. The burn-in process generally comprises forming a plasma within the chamber and using that plasma to remove the surface layer of material from the target.
A second conditioning process is known as pasting. Pasting generally applies a covering over material deposited on chamber components during a conventional PVD process. For example, PVD application of titanium nitride generally results in a layer of titanium nitride on the PVD chamber surfaces. The titanium nitride layer is typically brittle and may flake off during subsequent processes. Pasting generally applies a layer of titanium over the titanium nitride layer. The titanium layer substantially prevents the underlying titanium nitride from flaking or peeling. Typically, the chamber is pasted at predetermined intervals, such as after every 25 substrates are processed using a conventional titanium nitride PVD process. As with target burn-in, a shutter disk is disposed on the substrate support to prevent deposition of target material thereon during the pasting process.
Additionally, in PVD processes where titanium and titanium nitride are sequentially applied in-situ, the target requires cleaning prior to each titanium deposition to remove nitrides that may be present on the target from titanium nitride deposited on the prior substrate. Generally, target cleaning is similar to a burn-in process, having a few seconds duration, and includes protecting the substrate support with a shutter disk.
After completion of each burn-in, pasting and cleaning process, the shutter disk is rotated by a robotic arm disposed within the PVD chamber to a cleared position where the shutter disk does not interfere with the deposition process within the chamber. To center the position of the shutter disk, a sensor is employed on a shaft coupled to the robotic arm to detect the rotational position of the arm.
A problem with this arrangement for detecting the position of the shutter disk in the cleared position is that the sensor does not have the capability of confirming the relative position of the shutter disk to the robotic arm. For example, misalignment between the shutter disk and the robotic arm may result in a portion of the shutter disk remaining in the path of the ceramic substrate support. As the ceramic support is elevated into a process position, a portion of the substrate may contact the shutter disk, which may result in damage to the substrate or misalignment of the substrate on the ceramic support. Moreover, if the shutter disk comes in contact with the ceramic support, the ceramic support may become chipped or damaged and necessitate replacement. Additionally, if the shutter disk is not properly aligned on the robotic arm, the disk may be misaligned relative to the ceramic support during the burn-in and pasting process, thereby resulting in unwanted deposition on a portion of the ceramic support. Deposition material on the ceramic support may lead to particular generation, scratching of the wafer and a deterioration of process performance.
Therefore, there is a need for a PVD processing chamber having an improved shutter disk sensing system.